Physiological response and lipid metabolism induced by re-feeding in Jian carp (Cyprinus carpio var. Jian) subjected to short-term starvation.

The effects of starvation and re-feeding on Jian carp (Cyprinus carpio var. Jian) remain incompletely understood. This study investigated changes in growth performance, liver antioxidant capacity, intestinal morphology, fatty acid profile, and expression of genes related to lipid metabolism. Juvenile C. carpio var. Jian, with initial body weight of 29.50 ± 2.00 g, were reared in 15 cylindrical culture barrels (200L) at a stocking density of 10 fish per barrel. These fish were subjected to five feeding regimes: a continuous feeding group (control group, treatment A), complete fasting (treatment B), 1, 2, and 3 days starvation within one week, followed by re-feeding 6 days (treatment C), 5 days (treatment D), and 4 days (treatment E). The results indicated significantly lower growth performance in C. carpio var. Jian in treatments B and E compared to the control and treatment C (P < 0.05). Intestinal length (only 627 ± 13.14 μm in treatment B) was significantly reduced, and an increase in vacuoles was observed in C. carpio var. Jian with the prolonged starvation. Antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly (P < 0.05) improved in treatment C when compared with treatments B, D and E.. In contrast, malondialdehyde (MDA) value was lowest (12.62 ± 0.60 nmol/mL) in treatment B. Furthermore, continuous starvation significantly decreased the total lipid and fatty acids contents in the muscle (P < 0.05). Compared with the control group, the reduction of total lipid and fatty acids contents was 31.53 % and 4.57 %, respectively, particularly affecting n3PUFA and n6PUFA. However, after one-day re-feeding, these contents resumed. Lipid metabolism is closely related to fish health, while in the current study, the genes related to lipid metabolism including lipoprotein lipase (LPL), 6-phosphogluconate dehydrogenase (G6PD), and peroxisome proliferator-activated receptor alpha (PPARα) did not differ significantly in treatment C compared to the control group (P > 0.05). In contrast, expressions in treatments B, D, and E were significantly reduced (P < 0.05). Taken together, prolonged starvation (>one day per week) not only affected the growth, which may further disrupt the intestinal structure, weaken antioxidant capacity, but also attenuate lipid deposition.